Aura is life energy, and usually, it cannot leave the body. Energy can be released outside the body by Emission techniques, but the technique of En requires a different knack.
One creates the outer shell of En with a tough and flexible Ten, and expands the range by increasing the pressure inside with Ren like inflating a balloon. What is important here is the flexibility of Ten. For most Nen users, this film of Ten is too hard, so they cannot expand the range of En well. In that respect alone, it possesses properties closer to Transmutation than Emission. This is the reason why Emission users are not necessarily good at En.
The technique to emit aura far away. The technique to keep the film of Ten infinitely thin yet powerful. The technique to consider the created domain as an extension of one's own body and construct pseudo-sensory organs in the air. And the technique to process the enormous amount of gathered information and instantly select what is necessary. These are not things that can be learned just by training earnestly, nor are they techniques that can be handled without talent.
Chel is an Enhancer. Even in pure physical ability, she does not lag behind others. However, contrary to her bold and lazy behavior, her combat style excels in thorough information warfare. Long-term enemy detection with vast En is suitable for gathering information on the enemy camp and acts as a deterrent preventing careless intrusion into their own camp. She was a soldier who did not like fighting head-on and specialized most in ambushes.
Captain Gragg believes that if something happens to him, she is the one he can entrust with the succession with peace of mind. Her figure, instantly seeing through the advantages and disadvantages of the situation and dealing with it calmly, is like a cunning old wolf. But a crisis that caused even that first-class En user to show impatience was creeping up soundlessly.
"Toku, 5 o'clock direction, do you see anything?"
"...No, there are no abnormalities."
Chel asked one of the squad members, Tokunosuke. He was a Nen beast user. He could create numerous bird-shaped Nen beasts and let them fly around holding high-performance small cameras.
En allows one to recognize all objects within its range as if touching them with hands, but the information obtained thereby is different from the scene actually seen with eyes. Capturing visual images from cameras was also important.
However, the tablet Tokunosuke held showed nothing abnormal like Chel feared. There were too many places for an infiltrator to hide in the forest.
"Katroi, do you feel hostility?"
"Hii, d-don't tell me an enemy is approaching!?"
Katroi is an Emitter and handles enemy detection via En just like Chel. His En has a radius of about 30 meters. Compared to Chel, it pales, but generally, he is a user who can be called first-class enough. He is auxiliary personnel for when Chel cannot use En due to fatigue or other reasons.
However, his true value lay in his rare sensing ability rather than as an En user. Many Nen users possess excellent sensing abilities against enemy bloodlust. Masters do not overlook the slight bloodlust leaked by enemies hiding in the distance. Katroi's sense for this was outstanding. Contrary to his cowardly personality, or rather, precisely because of it, he was sensitive to malice directed at him from others.
Putting his personality aside, the whole squad placed their trust in his senses, which had an anecdote of seeing through a long-range snipe from 2 kilometers away. But judging from his reaction just now, it seems he hasn't sensed anything resembling hostility.
"Enemy?"
"No, I don't know yet... might be my imagination."
Chel didn't have proof either. Actually, there was no figure of a dangerous creature capturing them within her En. But, although it wasn't a definite sensation she could clearly call an abnormality, ever since entering the forest, she felt as if they were being tailed by someone.
The detection range of En is something any Nen user can see. So enemies don't often voluntarily stick their feet into the opponent's field. There are also ways to use it for containment by showing off the range of En.
However, just because they didn't step into the En didn't necessarily mean the enemy's existence couldn't be detected. Near the outer circumference of En, faint splashes of aura leaked from the film of Ten drift about, and an En user with keen senses can know of an enemy's approach without letting them step in.
This is common sense that Nen users should naturally know, and basic knowledge of tailing techniques. So a user with decent education would not let their guard down even outside of En and would follow while keeping a sufficient distance. The discomfort Chel was harboring now was close to the sensation of being clumsily tailed by an amateur Nen user.
Despite that, she hasn't been able to identify the opponent's existence. There is a possibility the enemy is hiding with high-level Zetsu. Many wild animals possess the ability of Zetsu from birth. Thinking that way, it wasn't strange, but the problem was that the opponent accurately grasped the range of En.
Unless one was a Nen user with open eye nodes, such a feat would be impossible. In fact, in previous expeditions, there were no creatures that saw through the detection range of En. If such an enemy existed, the unit would have been wiped out in the blink of an eye.
Yes, wiped out.
Chel rubbed the inner corners of her eyes hard, trying to loosen the stiffness in her thoughts. She felt as if Katroi's persecution complex had rubbed off on her. An illusion that wasn't there, shown by extreme stress. It was only an uncertain "hunch" that wouldn't be strange to dismiss as such. However, on the battlefield, there were many times when that baseless hunch had saved her life.
Chel reported the discomfort she sensed to her comrades. Upon doing so, she proposed two strategies.
One was to fold the En and quickly leave this place. It is a technique often used to shake off a tail. If the enemy is identifying their position relying on the range of En, cancelling that En can temporarily hide their whereabouts. Utilizing the 100-meter advantage to run as far as possible.
The disadvantage of this strategy is having to run through the unexplored lands of the Dark Continent with the wide-area detection ability called En sealed. And if they focused entirely on running, they wouldn't be able to know the enemy's true nature. Was there an enemy or not? What were they, and what characteristics did they have? They would be running about without knowing anything.
The other strategy was to conversely take the enemy inside the En. Decide the next countermeasure after knowing the enemy's information. The disadvantage is that it would provoke the enemy. It is unclear for what purpose they are tailing, but their response would surely change. If it came to combat, they wouldn't be able to return to the ship until the hostile force was neutralized. That meant a do-or-die operation.
"Use En. First, we get information."
The Captain made a swift decision. And Chel responded without interjecting negative opinions. Except for Katroi who was crying while grimacing pitifully, no one voiced an objection.
Chel used her ability "Unknown Fertility (Night Carpet)". This ability grants the effect of In to En. Theoretically, it is a composite of applied techniques and not a special ability, but its difficulty is at a level hard to realize. Even for her with her natural gift for En, it was a technique she could finally use by imposing various restrictions as an ability.
In other words, undetectable En. With this, she could take the enemy into the En without them realizing.
Chel's maximum range for En is 100 meters, but she doesn't always maintain that length. Usually, she saves some strength and keeps it around 80 meters. Meaning right now, the point where the enemy was thought to be loitering was well within the range of her En.
She extended additional En to that location. Moreover, only that extended portion became a state hidden by In due to the effect of "Unknown Fertility". Chel concentrated her entire spirit and activated En while fighting the load of the ability weighing on her whole body.
Then, she caught a shadow of something. A faint outline floated up. Because of the enemy's terrifying precision with Zetsu, the shape was not clear even though she had caught it inside her En. The size was about that of a human child, and there was one.
Just as she grasped that much, the enemy's figure vanished. It had escaped outside the En.
'I was noticed...?!'
It was something to be astonished by. In is a technique to cut off the presence of life energy emitted by aura. No matter how superior a beast's wild intuition, they shouldn't be able to feel even the residue of energy.
If one wanted to see through this, they had no choice but to use Gyo. A technique possible only for those who have opened their nodes, gained knowledge of Nen, and trained. Furthermore, the In Chel used was of a precision that could not be seen through by half-hearted Gyo.
A creature native to the Dark Continent well-versed in Nen. A threat against which even the single trump card allowed to humanity did not work. There was no logic by which they could win. That worst-case imagination filled her brain.
"Chel, what is it, what did you see... !?"
Her hesitation was long enough that the report was unintentionally delayed. However, from her complexion, the squad members guessed. The situation was progressing in a direction far worse than anticipated.
But, as if ignoring their agitation, a further change in the situation occurred.
The enemy that had escaped Chel's En entered into the En themselves. The movement was slow and calm. A complete change, showing off composure. Moreover, the enemy had deactivated Zetsu. Chel captured the shadow clearly.
It had the shape of a human. It had long hair reaching its waist. She was momentarily unsure due to the body shape like a child just after hitting puberty, but she guessed from the body lines that the gender was female.
"Visual, it's up!"
The camera on the Nen beast Tokunosuke operated finally displayed the full picture of the enemy.
Wearing not a single thread, the whole body was covered in mud and filthy. They understood the mud was intentionally smeared for camouflage. Amidst that, only the crimson eyes shone as if burning brightly. The way she walked while awkwardly swaying her thin limbs reminded them of a ghost that had crawled out from the depths of blood.
On her right hand, she carried a bizarre insect. The beetle, large enough to completely cover her right hand, was a color like dark, discolored liver blood. The figure of the insect clinging to the girl's arm without moving a muscle looked like an accessory used for suspicious sorcery.
However, unmistakably, that appearance was a human girl. Faced with a humanoid creature that appeared suddenly, the squad members couldn't help but be bewildered.
The girl turned her gaze toward the bird Nen beast. She seemed to understand she was being observed from there. She took action that made them feel clear intelligence.
She held up one finger. She moved the fingertip as if tracing the air. The girl used aura to write characters in the air. Nen users sometimes use aura invisible to the general public to leave characters like a code, attempting simple communication. It was a means of communication called Nen Writing.
'No hostility. Request dialogue.'
The language used was the common tongue generally used on the six continents. Using Nen as if it were natural, and even understanding human language. The Dark Continent survey, approaching its final stage, faced its greatest confusion here.